NEMA 7 cabinet purge: air or nitrogen?


Thread Starter


So if you have a control panel in a NEMA 7 cabinet with an explosion proof classification, how would you choose between the option of an air purge or nitrogen purge for a purge system? Is it the availability of compressed N2 or any other consideration? Thanks.
I'm sorry, you are right. No point in purging an explosion proof enclosure. For purging a NEMA 4, what is the reason to use air or nitrogen. Thanks.

> why would you purge a NEMA7 enclosure in the first place?

Ray Zimbal - MD&G+Controls

>For purging a NEMA 4, what is the reason to use air or nitrogen.

You need to be sure of utilize a purge rated NEMA enclosure, so that you have adequate sealing to control Nitrogen loss.
I think it would first of all be determined by what your source is i.e. you wouldn't purge with Nitrogen from bottles, but if you had a waste stream of dry Nitrogen 24/7, you might. otherwise air is the most common.

Another consideration is the panels location. if it's indoors, Nitrogen could present a safety hazard by displacing all the air.

I should add I have never seen anything but air used.

I would use air for purging as a matter of safety for maintenance personnel. I don't know how big your panel is but if it is opened by maintenance people and they are not aware they could breath in nitrogen from a nitrogen purged panel and be overcome by lack of oxygen.

S Venkataramanan

I agree with the statement that air is more safe. If we have to do maintenance in such panel then we must ensure that the panel is purged with air several times to achieve the oxygen level needed. That means long downtime.